Estimation of gas transport coefficients from differential permeation, integral permeation, and sorption rate data

Experimental methods for studying the transport of gases in polymers may be divided into three categories: integral permeation rate measurement, in which the cumulative amount of a penetrant that has passed through a membrane is determined; differential permeation rate measurement, in which the rate of penetration through a membrane is measured directly; and sorption rate measurement, or determination of the cumulative amount of a penetrant absorbed in a polymer sample. This paper reviews commonly used techniques for estimating diffusion coefficients from transport data of all three types. Several new estimation formulas are presented, and the relative merits of different measurement and estimation methods are discussed. A general relationship between the traditional time lag method for integral rate data analysis and a recently developed moment method for differential rate data analysis is established, extending the applicability of the moment approach to the analysis of non-ideal transport in membranes of arbitrary geometry and composition.     

Percolation and the colossal magnetoresistance of Eu-based hexaboride

Upon substituting Ca for Eu in the local-moment ferromagnet EuB6, the Curie temperature T(C) decreases substantially with increasing dilution of the magnetic sublattice and is completely suppressed for x相似文献   

Elliptic Quantum Groups and Ruijsenaars Models

We construct symmetric and exterior powers of the vector representation of the elliptic quantum groupsE _Τ,η(slN). The corresponding transfer matrices give rise to various integrable difference equations which could be solved in principle by the nested Bethe ansatz method. In special cases we recover the Ruijsenaars systems of commuting difference operators.     

Neue Antipodenpaare zur optischen Spaltung recemischer Basen

As new reagents for optical resolution of racemic bases the enantiomorphs of N-(1-phenyl-ethyl)-succinamic acid (I) and N-(1-phenyl-ethyl)-phthalamic acid (II) have been prepared. Optical resolution with I of (1-phenyl-ethyl)-amine, 2-amino-butane-1-ol, threo-1-(4-nitrophenyl)-2-amino-propane-1, 3-diol and with II of 1-phenyl-2-amino-propane is described.     

Spectra of Wess-Zumino-Witten models with arbitrary simple groups

We consider the Wess-Zumino-Witten two-dimensional sigma models with fields taking values in an arbitrary connected (but not necessarily simply connected) simple Lie groupG. The quantum states of the theory are realized geometrically as sections of a line bundle over the loop groupLG. The action of the current algebra of the theory is decomposed into highest weight representations by explicit construction of the highest weight states. This solves for the spectrum of the models. As a by-product, we obtain modular invariant partition functions of the theory on tori. The present paper extends the results of [7] where the casesG=SU(2) andSO(3) were treated.Ce rapport a été publié en partie grâce à une subvention du Fonds FCAR pour l'aide et le soutien à la rercherche     

A simple construction of ellipticR-matrices

We show that Belavin's solutions of the quantum Yang-Baxter equation can be obtained by restricting an infiniteR-matrix to suitable finite-dimensional subspaces. This infiniteR-matrix is a modified version of the Shibukawa-UenoR-matrix acting on functions of two variables.     

Broadly tunable mid-infrared VECSEL for multiple components hydrocarbon gas sensing

A new sensing platform to simultaneously identify and quantify volatile C1 to C4 alkanes in multi-component gas mixtures is presented. This setup is based on an optically pumped, broadly tunable mid-infrared vertical-external-cavity surface-emitting laser (VECSEL) developed for gas detection. The lead-chalcogenide VECSEL is the key component of the presented optical sensor. The potential of the proposed sensing setup is illustrated by experimental absorption spectra obtained from various mixtures of volatile hydrocarbons and water vapor. The sensor has a sub-ppm limit of detection for each targeted alkane in a hydrocarbon gas mixture even in the presence of a high water vapor content.     

3–4.5 μm continuously tunable single mode VECSEL

We present continuously tunable Vertical External Cavity Surface Emitting Lasers (VECSEL) in the mid-infrared. The structure based on IV?CVI semiconductors is epitaxially grown on a Si-substrates. The VECSEL emit one single mode, which is mode hop-free tunable over 50?C100?nm around the center wavelength. In this work, two different devices are presented, emitting at 3.4???m and 3.9???m, respectively. The lasers operate near room temperature with thermoelectric stabilization. They are optically pumped, yielding an output power >10?mW_p. The axial symmetric emission beam has a half divergence angle of <3.3^°.     

Zeros of Wronskians of Hermite polynomials and Young diagrams

For a certain class of partitions, a simple qualitative relation is observed between the shape of the Young diagram and the pattern of zeros of the Wronskian of the corresponding Hermite polynomials. In the case of the two-term Wronskian $W(H_n,H_{n+k})$, we give an explicit formula for the asymptotic shape of the zero set as $n\to \infty$. Some empirical asymptotic formulas are given for the zero sets of three-term and four-term Wronskians.